JP4100358B2 - Pre-phosphate steel plate and method for manufacturing the same - Google Patents

Description

  The present invention relates to a prephosphate steel plate and a method for manufacturing the same, which are preferably used for the body of an automobile.

  Zinc-based plated steel sheets are used for automobile bodies and the like for the purpose of improving their corrosion resistance and appearance. In the vehicle body manufacturing process of an automobile manufacturer or the like, since a vehicle body is manufactured by press forming a steel plate, it is desired that a zinc-based plated steel plate used for an automobile body or the like has excellent press formability. As a technique for obtaining a zinc-based plated steel sheet having this feature, a technique for improving lubricity by providing an iron-zinc alloy electroplating film on the upper layer of the zinc-based plating film is widely known. As a technique for improving the lubricity of the steel sheet surface, a technique for providing a phosphate film on the upper layer of a zinc plating film has been proposed. In addition, the phosphate film provided on the steel sheet surface before press forming is called “pre-phosphate film” as described in Non-Patent Document 1 (hereinafter, it has a pre-phosphate film on the surface layer of the steel sheet surface). Zinc-based plated steel sheets are sometimes simply referred to as “pre-phosphate steel sheets”.

Several techniques related to a process for forming a prephosphate film (hereinafter referred to as “prephosphate process”) have been disclosed so far. For example, Patent Document 1 discloses an upper layer of a zinc-based plating film. A technique is disclosed in which a pre-phosphate treatment is performed, and after the treatment, the pre-phosphate steel sheet is dried by washing with water (hereinafter, a treatment format through washing with water is referred to as “reactive treatment”). On the other hand, in Patent Documents 2, 3, 4, and 5, a treatment format in which the steel sheet is not washed with water after the pre-phosphate treatment but is dried as it is (hereinafter, a treatment method that does not undergo water washing is referred to as “coating type treatment”). )) Is disclosed. According to this coating type treatment, the influence of deterioration of the treatment liquid and fluctuations in treatment conditions is relatively small, and it is said that it is suitable for high-volume and high-speed treatment such as when treating steel strips. Among them, in Patent Documents 3 and 4, there is a technique for forming a film by a coating type treatment using a treatment liquid containing an oxide as a method for producing a prephosphate film as a condensed phosphoric acid film. Patent Document 5 discloses a technique for forming an amorphous coating containing Fe in the coating.
JP-A-7-138764 JP 2000-64054 A JP 2002-226976 A JP 2001-98383 A JP 2001-271153 A Japan Parkerizing Technical Report, Vol. 8, December 1995, p. 33-40

  However, the technique disclosed in Patent Document 1 has a problem that the influence of the treatment liquid and the treatment conditions on the amount of coating and the coating structure are relatively large. In addition, examples of the performance required for the prephosphate steel sheet include formability, weldability, and chemical conversion treatment. For example, the techniques disclosed in Patent Documents 3 and 4 have these performances. It was difficult to line up.

On the other hand, in recent years, for the purpose of reducing the weight of an automobile body, a high-tensile steel sheet having a tensile strength of 60 kg (580 MPa), 80 kg (780 MPa), or higher (hereinafter referred to as “high-tensile material”). ) Is being considered. However, when press-molding high-tensile galvanized steel sheets (currently, mainly galvannealed steel sheets (hereinafter referred to as “GA”)) are pressed, The surface pressure during the process becomes larger than when the base material is used as the base material, and the coating components stick to the mold and the plated pieces adhere to and accumulate on the mold, resulting in indentation defects in the molded product. There is concern that it will be easier to do. Furthermore, since this seizure places a burden on the mold, there is a problem that defects such as the removal of the cemented carbide film on the mold surface are likely to occur.
Thus, the high tension GA has a problem in formability as compared with the conventional GA. Therefore, in order to expand application to automobile bodies and the like, improvement and stabilization of the press formability of the steel sheet is desired.

  One of the factors affecting the press formability of a steel sheet is the slidability of the steel sheet surface. It is said that the better the slidability (qualitatively, the lower the coefficient of dynamic friction and the smaller the fluctuation), the more stable the press formability tends to stabilize. In such a case, improvement in slidability may be more important than evaluation of press formability.

  Therefore, an object of the present invention is to provide a pre-phosphate steel plate that can improve slidability and have good slidability, weldability, and chemical conversion treatment, and a method for manufacturing the same.

The present inventors investigated the relationship between the structure and manufacturing conditions of the prephosphate film and the slidability. As a result, it was first found that a certain amount of pre-phosphate coating was required to obtain a steel sheet having excellent slidability. However, it has been found that increasing the adhesion amount does not necessarily satisfy the slidability, but increasing the adhesion amount leads to a decrease in weldability. Therefore, when further investigation was made, the abundance ratio of P and Zn (II) in the very surface layer of the prephosphate film affected the slidability, and the larger the proportion of P, the better the slidability. I found. Furthermore, in order to obtain such a prephosphate film, it has been found that it is important to manage the strong electrolyte cation and anion concentration within a predetermined range as well as the acid concentration of the treatment liquid, and the present invention has been completed. .
The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

The invention according to claim 1 is a zinc-based plated steel sheet having a prephosphate film on at least one plated surface,
The adhesion amount of the prephosphate film is 1 mmol / m ² or more and 5 mmol / m ² or less in terms of P,
The molar ratio Zn / P of Zn and P contained in the prephosphate film is 1.0 or more and 2.0 or less,
The above problem is solved by a phosphate-coated zinc-based plated steel sheet, characterized in that the molar ratio Zn (II) / P of Zn (II) and P on the surface of the prephosphate film is less than 1.0. It is something to try.

According to invention of Claim 1, it becomes possible to provide the pre-phosphate steel plate which has favorable slidability and weldability.
Here, the “pre-phosphate film” refers to a phosphate film provided on the surface of a steel plate before press forming. Therefore, in the molar ratio Zn (II) / P of Zn (II) and P on the surface of the prephosphate film, the denominator P does not become zero.

  The invention according to claim 2 is the phosphate-coated zinc-based plated steel sheet according to claim 1, wherein the prephosphate film has a crystalline hopite and an amorphous phosphate. It is characterized by that.

  The invention according to claim 3 is the phosphate-coated zinc-based plated steel sheet according to claim 1 or 2, wherein the prephosphate film substantially does not contain Ni, Mn, and Fe. .

  According to invention of Claim 3, it becomes possible to provide the pre-phosphate steel plate which has favorable chemical conversion treatment property.

  The invention according to claim 4 is the phosphate-coated zinc-based plated steel sheet according to any one of claims 1 to 3, wherein the tensile strength is 580 MPa or more.

  According to the fourth aspect of the present invention, it is possible to provide a high-tensile zinc-based plated steel sheet that can have good slidability, weldability, and chemical conversion treatment.

The invention according to claim 5 is a method for producing a phosphate-coated galvanized steel sheet,
A first step of bringing a phosphating solution into contact with at least one surface of the galvanized steel sheet;
A second step of drying the steel sheet contacted with the treatment liquid without washing with water after the first step;
The treatment liquid contains a phosphate group of 0.3 to 1.0 mol / L and zinc ions having a molar ratio of 0.5 or less to the phosphate group,
The total acid concentration T.I. A. And free acid concentration F.V. A. The acid ratio represented by the ratio is 4.5 or more and 6.5 or less,
The strong electrolyte anion concentration [A ^m− ] (m: anion charge) and the strong electrolyte cation concentration [M ^{n +} ] (n: cation charge) in the treatment liquid satisfy the relationship of the formula (1). The above-mentioned problem is to be solved by a method for producing a phosphate-coated zinc-based plated steel sheet.
Σ (n × [M ^{n +} ]) − Σ (m × [A ^m− ])> 0 (1)

The invention according to claim 6 is a method for producing a phosphate-coated galvanized steel sheet,
A first step of bringing a phosphating solution into contact with at least one surface of the galvanized steel sheet;
A second step of drying the steel sheet contacted with the treatment liquid without washing with water after the first step;
The treatment liquid contains 0.3 to 1.0 mol / L of phosphate groups and zinc ions having a molar ratio of 0.5 or less with respect to the phosphate groups,
The total acid concentration T.I. A. And free acid concentration F.V. A. The acid ratio represented by the ratio is 4.5 or more and 6.5 or less,
T.A. A. And F. A. The zinc ion concentration [Zn ²⁺ ] satisfies the relationship of the formula (4), and is intended to solve the above problem by a method for producing a phosphate-coated zinc-based plated steel sheet.
T.A. A. -2 × F. A. − (14/5) × [Zn 2 ⁺ ]> 0 (4)

  According to invention of Claim 5 or 6, the method of manufacturing easily the pre-phosphate steel plate which can arrange favorable slidability, weldability, and chemical conversion treatment property is provided.

  The invention according to claim 7 is the method for producing the phosphate-coated zinc-based plated steel sheet according to claim 5 or 6, wherein the treatment liquid adhered to the steel sheet between the first step and the second step. It has the process of reducing this.

  According to invention of Claim 7, the manufacturing method of the pre-phosphate steel plate which can dry the film on the steel plate surface in a short time is provided.

  According to the pre-phosphote steel sheet and the manufacturing method thereof of the present invention, in the pre-phosphate steel sheet that is useful as a steel sheet for automobile bodies, the slidability is improved and good slidability, weldability, and chemical conversion treatment are performed. Therefore, it is possible to provide a method for easily manufacturing a prephosphate steel plate having the characteristics.

In the present invention, a predetermined prephosphate film is formed on the plated surface of a zinc-based plated steel sheet. Embodiments of the present invention will be described below.
1. Zinc-based plated steel sheet In the present invention, the type of plating is not particularly limited as long as the intended prephosphate film can be obtained. At present, alloyed hot-dip galvanized steel sheets that are widely used in automotive applications are preferred, but hot-dip galvanized steel sheets (not alloyed) and electrogalvanized steel sheets that are expected to be used in automotive applications in the future are also available. It can be used.
In addition, the amount of plating or the like is not particularly limited. However, from the viewpoint of workability and weldability, the plating adhesion amount is preferably 150 g / m ² or less.
Furthermore, the present invention is useful for high-tensile materials that are inferior in moldability compared to conventional materials. For example, it is useful for proceeding with the application of high-tensile steel sheets having a tensile strength of 60 kg (580 MPa), 80 kg (780 MPa), or higher, which are currently under investigation.

2. Prephosphate film 2-1 Structure of film The average molar ratio of Zn and P of the prephosphate film in the present invention (hereinafter referred to as “Zn / P”) is 1.0 or more and 2.0. The following. This value is almost equal to the Zn / P stoichiometric ratio (= 1.5) in zinc phosphate Zn ₃ (PO ₄ ) ₂ .
In addition, the prephosphate film | membrane obtained by the method of this invention is observed as a substantially crystalline film | membrane about what Zn / P is 1.0 or more. On the other hand, since the prephosphate film of the present invention is formed by a coating-type treatment, there is a portion (mainly amorphous phosphate) where the treatment solution is dried as it is to form a film. Including this part, the average Zn / P of the entire prephosphate film is 1.0 or more and 2.0 or less.

  In general, the prephosphate film generally contains metal elements other than Zn, such as Ni, Mn, and Fe, as disclosed in Patent Document 1. Moreover, in patent document 5, Fe is contained as an essential component. However, in the present invention, it is preferable that Ni, Mn, Fe and the like are not substantially contained in the film. This is due to the following reason.

In most cases, the prephosphate steel sheet is finally painted after the forming process. In automobile manufacturers, etc., zinc phosphate treatment is applied as a paint base treatment. In order to form a sound ground treatment layer, it is better that the pre-phosphate film does not exist at that time. For that purpose, the pre-phosphate film is removed in the degreasing step prior to the ground treatment. It is better (hereinafter, the ease of removal of the prephosphate film in the degreasing step is referred to as “film removal property”). When Ni, Mn, Fe or the like is contained in the film, the film removal property tends to deteriorate. Therefore, it is preferable that Ni, Mn, Fe, or the like is not substantially contained in the prephosphate film for applications such as those described above after coating.
Here, in the present invention, “substantially free of Ni, Mn, Fe, etc.” means that the total amount of elemental components such as Ni, Mn, Fe, etc. in the prephosphate film is 1% by mass or less. Say something.
In the case of a prephosphate film substantially free of Ni, Mn, Fe, etc., even if the film is not completely removed in the degreasing process and remains slightly, the etching of the steel sheet surface in the subsequent ground treatment process is changed. Since it is activated, a good paint ground layer can be obtained. Therefore, the pre-phosphate film having the above characteristics is effective when the degreasing liquid or the coating surface treatment liquid is deteriorated, or when the surface treatment of a processed product having a portion where the chemical liquid is difficult to flow due to the shape is performed. .

2-2 Amount of film adhesion The amount of adhesion of the prephosphate film in the present invention is essential to be 1 mmol / m ² or more and 5 mmol / m ² or less (approximately 30 to 160 mg / m ² ) in terms of P. This is because it is preferably 1 mmol / m ² or more from the viewpoint of ensuring slidability, and is preferably 5 mmol / m ² or less from the viewpoint of preventing deterioration of continuous spot property during spot welding. More preferably, the coating amount of the film is ² to 4 mmol / m ² .

2-3 Surface Structure of Film In the present invention, the molar ratio of Zn (II) to P (hereinafter referred to as “Zn (II) / P”) in the very surface layer of the prephosphate film is 1.0. Less than. This is because the lower the Zn (II) / P, the better the slidability. Since the required slidability may vary depending on the actual pressing method and shape, the threshold value of Zn (II) / P may vary accordingly, but Zn (II) / P is less than 1.0. If so, the slidability is generally good. In addition, it is preferably less than 1.0, more preferably less than 0.9, from the viewpoint of preventing material cracking and die seizure in the press molding process.

The reason why the slidability is improved by making Zn (II) / P less than 1.0 is not clear, but the surface state of the film under the conditions is expressed by the formulas (i) to (iii) described later. It is considered that the chemical reaction does not proceed so much and the activity of the film surface is high. It is considered that this highly active state promotes chemical adsorption of lubricating oil and rust preventive oil on the surface of the film, and forms a lubricating film with good slidability.
In addition, when investigating Zn on the surface of the film by X-ray photoelectron spectroscopy analysis (hereinafter referred to as “XPS”) described later, a peak attributed to metal Zn and a peak attributed to Zn (II) are detected. Therefore, these are peak-separated and Zn (II) / P is obtained from the peak due to Zn (II).

3. 3-1 Pre-cleaning method In the manufacturing method of the prephosphote steel plate of the present invention, in order to ensure the reactivity of the surface of the plated steel plate substrate in the prephosphate treatment of the steel plate, It is necessary that the covering oxide and dirt are removed. As the oxide covering the surface of the galvanized steel sheet, zinc oxide, aluminum oxide, and the like are assumed. In order to remove these efficiently, it is preferable to use an alkaline or acidic aqueous solution. For example, an aqueous solution based on a sodium hydroxide aqueous solution, a hydrochloric acid aqueous solution, or the like can be used. In particular, in the case of a hot dip galvanized steel sheet, the surface is often covered with aluminum oxide, and for the purpose of removing the oxide, a cleaning solution based on an alkaline aqueous solution such as an aqueous sodium hydroxide solution should be used. Is preferred.

3-2 Surface Adjustment After the pre-cleaning step, it is preferable to further adjust the surface in order to uniformly homogenize the plating surface and uniformly deposit the prephosphate film. The plated steel sheet is usually subjected to temper rolling. In this case, the activity of the plating surface becomes non-uniform between the contact part / non-contact part with the rolling roll, etc., and during the pre-phosphate treatment. This is because uneven reaction tends to occur. Examples of the surface conditioning treatment include immersion treatment in a titanium colloid-containing aqueous solution, a zinc phosphate colloid-containing aqueous solution, and the like.

3-3 Prephosphate treatment The prephosphate treatment in the method for producing a prephosphate steel sheet according to the present invention is carried out by using phosphate groups (PO ₄ ³⁻ , H ₂ PO ₄ ⁻ , HPO ₄ ²⁻ , H ₃ PO ₄ as main components). ) And zinc ions are brought into contact with the plated steel sheet, and then a pre-phosphate film is formed on the surface layer of the zinc-based plated steel sheet by a coating type treatment that is dried without washing with water. The method for obtaining the prephosphate steel sheet of the present invention is not particularly limited except that it is a coating type treatment, but preferred embodiments will be described below.

<Processing format>
In the present invention, a prephosphate steel sheet is manufactured by a so-called coating type treatment. Examples of the application method include a spray ringer method in which the treatment liquid is sprayed and then the excess treatment liquid is squeezed, and a roll coating method in which the treatment liquid is transferred from the applicator roll to the steel material. Comparing these two methods, from the viewpoint of maintaining the mass balance of the treatment liquid, the roll coating method with less return of the treatment liquid in contact with the steel plate is more advantageous. Among the roll coating methods, the reverse coating method is particularly advantageous. There is little return and is advantageous. On the other hand, from the viewpoint of productivity during continuous operation, the spray ringer method is more advantageous because the wear of the ringer roll is less. In particular, when the peripheral speed of the ringer roll is synchronized with the sheet passing speed of the steel sheet (including the case where the ringer roll is not driven and the roll peripheral speed and the sheet passing speed substantially coincide), roll wear reduction is achieved. Is advantageous. Therefore, the roll coat method is advantageous for small-scale production, while in mass production, it is preferable to operate by the spray ringer method after adding a system for maintaining the mass balance of the chemical solution.

<Processing liquid>
In the present invention, the phosphate group content in the prephosphate treatment solution is preferably in the range of 0.3 to 1.0 mol / L. The molar ratio of zinc ions to phosphate radicals is preferably less than 0.5, more preferably 0.35 or more and less than 0.5. This is mainly due to the fact that the range is suitable for the coating amount within the range of the present invention, and when the zinc ion concentration becomes too high, zinc phosphate sludge is generated in the chemical solution. This is because the surface quality is adversely affected.

  Furthermore, the acid ratio (TA / FA) derived from the total acid concentration (TA) and free acid concentration (FA) of the treatment liquid is also important. From the viewpoint of preventing an increase in the amount of Zn eluted from the surface and reducing the rapid precipitation of the prephosphate film, the preferred range of the acid ratio is 4.5 to 6.5.

In the coating type treatment of the present invention, in order to obtain a galvanized steel sheet having a prephosphate film excellent in slidability, strong electrolyte anions ^Am- and zinc ions except for phosphate ions in the treatment liquid bath are removed. The relationship of the concentration of the strong electrolyte cation M ^{n +} is adjusted so as to satisfy the following formula (1). As a result, the Zn (II) / P value on the surface of the prephosphate film is generally less than 1.0, and the slidability is improved.
δ≡Σ (n × [M ^{n +} ]) − Σ (m × [A ^m− ])> 0 (1)
However, [Am ⁻ ]: Am ⁻ concentration (mol / L)
m: charge of anion
[M ^{n +} ]: M ^{n +} concentration (mol / L)
n: The charge of the cation.

Strong as the electrolyte anions A ^m-, as will be described later, and a fluoride ion such as nitrate ion or etching agent as Fukukyokuzai. In other words, these strong electrolyte anions are treatment liquids and anions for achieving processability, excluding phosphate ions added to the liquid as a prephosphate film component. Moreover, as strong electrolyte cation ^{Mn +} , the ammonium ion, sodium ion, etc. in the alkaline aqueous solution (For example, sodium hydroxide aqueous solution and ammonia aqueous solution) mainly added when adjusting the said acid ratio are mentioned. In other words, these strong electrolyte cations are added concomitantly in order to establish treatment liquid and treatment properties, excluding cations added to the liquid as a prephosphate film component, such as zinc, iron, nickel, and manganese. It is a cation.

  When the relationship between the strong electrolyte cation and the strong electrolyte anion does not satisfy the above formula (1), that is, when the amount of the strong electrolyte cation in the treatment liquid is insufficient, Zn (II) / P The composition becomes large and adversely affects the slidability. The reason why the amount of the strong electrolyte cation affects the surface composition of the prephosphate film is not clear, but for example, the following mechanism is conceivable.

That is, the prephosphate reaction includes an etching reaction of the following formula (i) and a hydrolysis reaction of the following formulas (ii) and (iii).
Zn (plating film) + 2H ₃ PO ₄ → Zn ²⁺ + 2H ₂ PO ₄ ⁻ + H ₂ ↑ (i)
Zn ²⁺ + 2H ₂ PO ₄ ⁻ → ZnHPO ₄ ↓ + H ₃ PO ₄ (ii)
3ZnHPO ₄ → Zn ₃ (PO ₄ ) ₂ ↓ (hopeite) + H ₃ PO ₄ (iii)
As the reactions (i) to (iii) proceed, the phosphate radicals in the treatment liquid are consumed and decreased. At this time, it is considered that the reactions (ii) and (iii) stop when the unreacted phosphate radical and the excess strong electrolyte cation in the treatment liquid reach an equivalent amount as an acid / base. As a result, in the dry film forming process, for example, a salt in which a strong electrolyte cation and a phosphate group are bonded is generated in the vicinity of the prephosphate film, and as a result, the value of Zn (II) / P on the surface layer is considered to be small. . As described above, the surface in such a state is assumed to be highly active and have a high adsorptivity with the lubricating oil or the rust preventive oil, which is considered to lead to a sliding improvement effect.

On the other hand, F.V. A. And T. A. Is represented by the following equation.
F. A. = [PO ₄ ] + Σ (m × [A ^m− ]) − 2 × [Zn ²⁺ ] −Σ (n × [M ^{n +} ]) (2)
T.A. A. = F. A. + [PO ₄ ] + (4/5) × [Zn ²⁺ ] (3)
However, [PO ₄ ]: the concentration of phosphate radicals in the treatment liquid [Zn ²⁺ ]: the concentration of Zn (II) in the treatment liquid.

From the above formulas (1) to (3), the formula (1) can also be expressed in the form of the following formula (4).
δ = Σ (n × [M ^{n +} ]) − Σ (m × [A ^m− ])
= T. A. -2F. A. − (14/5) × [Zn 2 ⁺ ]> 0 (4)
A more preferable value of δ is 0.05 or more.

Other conditions will also be described.
As a component other than the above in the prephosphate treatment liquid, it is preferable to contain nitrate ions (NO ₃ ⁻ ) as a depolarizing agent in a molar ratio with respect to the phosphate radical of 0.05 or more and 0.5 or less. Further, an etchable fluoride (for example, hydrofluoric acid, fluorosilicic acid, fluoroboric acid, etc.) is contained so that the molar ratio with respect to phosphate ions is 0.05 or more and 0.5 or less in terms of hydrofluoric acid. It is preferable. If the amount of these components is too small, the rate of progress of the reactions (i) to (iii) is low, and it is difficult to obtain the film intended by the present invention in a short time. On the other hand, the inclusion of these components affects the direction of increasing the value of δ.

  Further, as described above, since it is preferable that the prephosphate film does not substantially contain Ni, Fe, Mn and the like, it is preferable that these elements are not contained in the treatment liquid as much as possible. Under continuous operation, components eluted from the steel strip and equipment are mixed in the film, and therefore the content of these elements in the treatment liquid is preferably 100 ppm or less in total.

Example 1
<Preparation of pre-phosphate steel plate>

As shown in Tables 1 and 2, the pre-cleaning and surface conditioning treatments were performed on the alloyed hot-dip galvanized steel sheet (plate thickness 0.8 mm, plating coating amount: about 45 g / m ² per side). Pre-phosphate treatment was performed by a spray ringer method using a pre-phosphate treatment solution that was appropriately changed to produce a pre-phosphate steel plate. The main prephosphate treatment conditions and the analysis method of the prephosphate treatment solution are as follows.
Pre-phosphate treatment conditions Pre-cleaning conditions: Immerse in a 7% NaOH aqueous solution (70 ° C.) for 5 seconds, and then wash with water after immersion.
Surface adjustment treatment: Immersion in 1 g / L liquid (normal temperature) of Percolen Z (manufactured by Nihon Parkerizing Co., Ltd.) for 10 seconds.
-Analyzing method of prephosphate treatment liquid A predetermined amount of the treatment liquid was infiltrated into a filter paper to make a sample, and the phosphoric acid concentration and the zinc ion concentration were quantitatively analyzed using a fluorescent X-ray analyzer. Total acid concentration (TA) and free acid concentration (FA) were measured by acid / base titration. From the measured values of total acid concentration (TA), free acid concentration (FA), and zinc ion concentration, δ in Table 1 was calculated using the above equation (4).
<Evaluation of prephosphate treatment solution>
Film analysis and performance evaluation were performed on the samples of the prephosphate steel plate obtained as described above. A method for analyzing the prephosphate film and a method for evaluating the performance are shown below.

Measurement of adhesion amount of prephosphate film, bulk composition analysis Only 5% chromic acid aqueous solution was used to dissolve the prephosphate film, and P and Zn in the solution were quantitatively analyzed by atomic absorption spectrometry.

・ Surface composition analysis of prephosphate film Measure the integrated intensity of each spectrum of Zn and P on the prephosphate film surface by XPS method (evaluation area: 5mm × 5mm) and calculate the value of Zn (II) / P did. For the Zn peak, the metal Zn peak and the Zn (II) peak were separated, and the value of Zn (II) alone was used.

・ Slidability Evaluation Method According to the pin-on-disk test method described in Japanese Patent Application Laid-Open No. 2003-136151, the friction coefficient is measured under the following conditions in a state where rust preventive oil is applied, and the friction coefficient and the variation of the friction coefficient are measured. From this, the slidability was evaluated.
Test conditions;
Pressing load: 30N Test tool tip shape: Ball Test tool tip shape Curvature: 2.5mmR Test tool tip material: SKD steel Test temperature: 60 ° C Turning radius: 10mm
Sliding speed: 63 mm / min (1 rpm) Number of sliding times: 20 rotations Friction coefficient μ: Maximum value of 20 average values calculated from 12 measured values per rotation Friction coefficient variation ν: The maximum friction coefficient is Standard deviation value of 12 measurement results in the obtained rounds Evaluation criteria;
X: μ is 0.15 or more x: μ is less than 0.15 and B is 0.04 or more ○: μ is less than 0.15 and B is less than 0.04

-Spot weldability evaluation method Spot welding was performed using a spot welder under the following conditions, and the number of hits until the nugget diameter (mm) was smaller than 4√t (t: steel plate thickness (mm)) was evaluated. .
Electrode: Domed electrode Applied pressure: 2450N
Energizing time: 12 cycles (frequency is 50 Hz)
Welding current: The minimum current at which dust starts to occur is investigated in advance and set to that current.
Evaluation criteria;
○: More than 3000 hit points ×: Less than 3000 hit points

Chemical conversion treatment evaluation method The sample was subjected to the following alkaline degreasing, water washing, and surface conditioning treatments, and then subjected to chemical conversion treatment (zinc phosphate treatment) under the following conditions. The surface of the obtained chemical conversion treatment material was observed with a scanning electron microscope (SEM) to investigate the chemical conversion treatment property.
Degreasing conditions: Immerse in fine cleaner 4380 (Nihon Parkerizing Co., Ltd.) 200 g / l liquid (50 ° C.) for 2 minutes
Surface adjustment conditions: Dipping for 10 seconds in 1 g / L liquid (room temperature) of Percolen Z (manufactured by Nihon Parkerizing Co., Ltd.).
Chemical conversion treatment conditions: PB-3080 (manufactured by Nihon Parkerizing Co., Ltd., liquid temperature 43 ° C.) sprayed for 2 minutes.
Evaluation criteria;
○: Chemical crystal grains of about 1 μm are densely precipitated.
X: Crystals are sparsely precipitated.
X: The size of the crystal grains is not uniform.
X: The crystal grain is coarse.
The results of film analysis and performance evaluation of this example are shown in Tables 1 and 2 (Nos. 1 to 24). Hereinafter, the pre-phosphote steel sheet of the present invention is described as “the steel sheet of the present invention”, and the steel sheet that is not the pre-phosphate steel sheet of the present invention is described as “a steel plate of a comparative example”.

  From Tables 1 and 2, the steel plates of the present invention (Nos. 5, 6, 9, 10, 17 to 24) were all good because the evaluations of slidability, spot weldability, and chemical conversion treatment were all good. The result that the slidability, the weldability, and the chemical conversion treatment property are arranged side by side was obtained. On the other hand, the steel plate of the comparative example is evaluated for slidability when the amount of the prephosphate coating is small (No. 1 and No. 2) and when the surface layer Zn / P value is 1 or more (No. 13 to 16). Became x, and the slidability was inferior. On the other hand, when there was too much film | membrane adhesion amount (No. 3, 4, 7, 8, 11, 12), spot weldability evaluation became x and weldability was inferior. In addition, chemical conversion property was favorable in all the steel plates used in the present Example. This is presumably because Ni, Mn, Fe, etc. are not substantially contained in the prephosphate treatment solution and are not contained in the film. In all the steel plates used in this example, the bulk Zn / P value was stable at about 1.5. Furthermore, according to the production method of the present invention, it was possible to stably produce a prephosphate steel plate (the steel plate of the present invention) that can have good slidability, weldability, and chemical conversion treatment.

(Example 2)
A hot dip galvanized steel sheet (plate thickness 0.8 mm, adhesion amount 90/90 (g / m ² )) is subjected to the same pre-cleaning and surface conditioning treatment as in Example 1, and then subjected to pre-phosphate treatment by a roll coating method. The performance was evaluated. The prephosphate conditions are as shown in Tables 3 and 4. On the other hand, the evaluation method is substantially the same as in Example 1, but the evaluation criteria for spot weldability are as follows.
-Evaluation standard of spot weldability (circle): 1000 points or more x: Less than 1000 points The result of the film | membrane analysis and performance evaluation of a present Example is shown according to Table 3 and Table 4 (No. 25-33).

From Table 3 and Table 4, even when the base material is GI (hot dip galvanized steel sheet), the steel sheets (No. 28, 29, 31 to 33) of the present invention have good slidability, weldability, and chemical conversion treatment. The result that the sex can be arranged side by side was obtained. On the other hand, the result that the slidability was inferior was obtained for the steel plates (Nos. 25 to 27, 30) of the comparative examples in which the value of the surface layer Zn (II) / P was 1 or more.

Claims (7)

A zinc-based plated steel sheet having a pre-phosphate film on at least one plated surface,
The adhesion amount of the prephosphate film is 1 mmol / m ² or more and 5 mmol / m ² or less in terms of P,
The molar ratio Zn / P of Zn and P contained in the prephosphate film is 1.0 or more and 2.0 or less,
A phosphate-coated zinc-based plated steel sheet, wherein the molar ratio Zn (II) / P of Zn (II) and P on the surface of the prephosphate film is less than 1.0. The phosphate-coated zinc-based plated steel sheet according to claim 1, wherein the prephosphate film has a crystalline hopite and an amorphous phosphate. The phosphate-coated zinc-based plated steel sheet according to claim 1 or 2, wherein the pre-phosphate film substantially does not contain Ni, Mn, and Fe. The phosphate-coated zinc-based plated steel sheet according to any one of claims 1 to 3, wherein the tensile strength is 580 MPa or more. A method for producing a phosphate-coated galvanized steel sheet,
A first step of bringing a liquid containing a phosphate into contact with at least one surface of a zinc-based plated steel sheet;
And a second step of drying the steel sheet in contact with the liquid without washing after the step,
The liquid contains a phosphate group of 0.3 to 1.0 mol / L and zinc ions having a molar ratio of 0.5 or less with respect to the phosphate group,
The total acid concentration T.I. A. And free acid concentration A. The acid ratio represented by the ratio is 4.5 or more and 6.5 or less,
The strong electrolyte anion concentration [A ^m− ] (m: anion charge) and the strong electrolyte cation concentration [M ^{n +} ] (n: cation charge) in the liquid satisfy the relationship of the formula (1). A method for producing a phosphate-coated zinc-based plated steel sheet.
Σ (n × [M ^{n +} ]) − Σ (m × [A ^m− ])> 0 (1) A method for producing a phosphate-coated galvanized steel sheet,
A first step of bringing a liquid containing a phosphate into contact with at least one surface of a zinc-based plated steel sheet;
And a second step of drying the steel sheet in contact with the liquid without washing after the step,
The liquid contains a phosphate group of 0.3 to 1.0 mol / L and zinc ions having a molar ratio of 0.5 or less with respect to the phosphate group,
The total acid concentration T.I. A. And free acid concentration A. The acid ratio represented by the ratio is 4.5 or more and 6.5 or less,
The T.A. A. And F. A. And zinc ion concentration [Zn ^<2+ >] satisfy | fill the relationship of Formula (4), The manufacturing method of the phosphate covering zinc-type plated steel plate characterized by the above-mentioned.
T.A. A. -2 × F. A. − (14/5) × [Zn 2 ⁺ ]> 0 (4) The phosphate-coated zinc system according to claim 5 or 6, further comprising a step of reducing the liquid adhering to the steel plate between the first step and the second step. Manufacturing method of plated steel sheet.